The invention relates to an apparatus for treating a layer of material, particularly in a number of thermal treatment phases succeeding one another in time with different treatment temperatures and durations.
In the food industry, in particular, there are processes in which a product is subjected to a number of successive thermal treatment phases, such as pasteurisation, sterilisation, uperisation, drying, roasting, crystallisation and the like, each being carried out in a layer. Such treatment phases generally differ from one another essentially in the temperature at which they are to be effected and the time they should last and alos the course of the temperature during the treatment phases. In order to effect the thermal treatment phases with satisfactory results, suitable structure of the layer of material is of critical importance, such as a homogeneous particle size which is obtained by preliminary mechanical treatment, e.g. grinding.
Moreover, in the food industry, the material in question is a delicate organic material, and various requirements concerning the flavour, aroma, hygiene, etc., are imposed on the finished product. In addition, the material to be processed is often of varying quality, so that, when the individual treatment phases are carried out, the particular quality of the material in question has to be taken into account, by modifying the treatment parameters, in order to obtain a product of the customary desired quality.
To carry out the individual successive treatment phases, corresponding pieces of apparatus designed specifically for the particular treatment phase to be effected are usually combined one after another to form a production line.
This takes up a relatively large production area and requires additional transporting means for transferring the material to the next piece of apparatus, thus resulting in hygiene problems and heat losses. The number of staff required is also considerable.